1. Field of the Invention
The disclosed and claimed concept relates to a conversion system and, more specifically, to a multi-out conversion system utilizing a crankshaft associated with each end lane or tab, wherein the lanes are isolated portions of the total load thereby reducing and aligning the applied load per crankshaft.
2. Background Information
Metallic containers (e.g., cans) for holding products such as, for example, food and beverages, are typically provided with an easy open can end on which a pull tab is attached (e.g., without limitation, riveted) to a tear strip or severable panel. The severable panel is defined by a scoreline in the exterior surface (e.g., public side) of the can end. The pull tab is structured to be lifted and/or pulled to sever the scoreline and deflect and/or remove the severable panel, thereby creating an opening for dispensing the contents of the can.
A can end consists of a shell and tab. The shell and the tab are made in separate presses. The shell is created by cutting out and forming the shell from a coil of sheet metal product (e.g., without limitation, sheet aluminum; sheet steel). In a separate press, tabs for the can end are produced by feeding in a continuous coil through a tab die. The shells and tabs are conveyed to a conversion press. At the conversion press, the blank shell is fed onto a belt which indexes through an elongated, progressive die known as a lane die. The lane dies include a number of tooling stations which form the paneling, score and integrated rivet on the shell. The lane dies are part of an upper tooling assembly and a lower tooling assembly. The tabs move longitudinally through the die(s). The longitudinal axes of the tab die(s) are disposed generally perpendicular to the longitudinal axes of the lane dies. At the final tool station, the tab is coupled to the shell thereby creating the can end.
Typically, each tool station of the conversion press includes an upper tool member, which is structured to be advanced towards a lower tool member upon actuation of a press ram. The shell is received between the upper and lower tool members. Alternatively stated, the shell is received between the upper and lower tool assemblies. The upper tool assembly is structured to reciprocate between an upper position, spaced from the lower tool assembly, and a lower position, adjacent the lower tool assembly. Thus, the upper tool member engages the shell when the upper tool assembly is in the second position and the upper and/or lower tool members, respectively, act upon the public and/or product (e.g., interior side, which faces the can body) sides of the shell, in order to perform a number of the aforementioned conversion operations. Upon completion of a cycle, the press ram retracts the upper tool assembly and the partially converted shell is moved to the next successive tool station, or the tooling is changed within the same station, to perform the next conversion operation.
As noted above, the conversion press is, typically, structured to process multiple can ends at one time. That is, the conversion press includes multiple lane dies defining separate “lanes.” Each lane includes successive tool stations. It is common to include an even number of lanes, e.g., four lanes. The successive tool stations in each lane may be identical or different. Generally, the first tool station in each lane performs a forming operation such as forming a bubble, or, first formation to create the integrated rivet. This operation requires a high force, but the location of the application of force is furthest away from ram resulting in the highest tipping moment.
The conversion press typically includes a single elongated ram that operates all die sets. The ram applies a total superposition of force(s) of about 80 tons. Rams capable of providing such forces are large and require a large drive assembly as well. This force is applied along the longitudinal axis of the ram. The ram is typically coupled to a central location on a die shoe that supports the upper tool members. Thus, when there are four lanes, the ram is attached between the two central lanes and offset from all tool stations. In this configuration, the ram, the die shoe and the linkages therebetween are subjected to multiple loads and moment arms that are unbalanced. That is, because the ram is not aligned with any single lane, there are various tipping moments (i.e. torque) applied to the ram, the die shoe and the linkages therebetween that would not be present, or would be lower, if the conversion press had a single lane and the press ram was aligned with the lane.
The forces on the ram, the die shoe and the linkages therebetween are further unbalanced because the bubble operation at the first tool station creates a greater tipping moment than subsequent tool stations. That is, while the bubble operation may not need the greatest force, because this operation occurs at the first tool station, the distance from the center of the tool lane die is greater than for other tool stations. Thus, the distance multiplied by a large force creates the largest tipping moment. The tab lane die, however, is subjected to lesser forces and, as such, the loads and tipping moments cause fewer problems with regard to the tab lane die assembly. The tab lane, however, does create tipping moments on the ram when the ram actuates the tab lane die. That is, by virtue of being coupled, and spaced, from the ram, the ram and other elements are subject to wear and tear due to the tab lane die assembly even though the tab lane die assembly is relatively unaffected by those same forces. The large force required to operate the conversion press, as well as the unbalanced load, cause these elements to deflect, thereby causing wear and tear on the ram, the end lane die assemblies, including the die shoe, and the linkages therebetween.
Further, the ram is, typically, disposed above the die shoe and tooling stations. Generally, it is easier to construct a ram assembly above the tooling elements than to provide space for the ram below the tooling elements. Thus, the ram is, typically, disposed above the can ends being formed. In this configuration, lubricants and cooling fluids used in/on the ram may drip on the can lids.
A specific example is disclosed in Appendix A wherein, as shown in Figure A, a conversion press includes three lanes, lanes A, B, and C. Each end lane typically includes eight tooling stations and each tab lane typically includes seventeen tooling stations. As shown in the table data at page 1, the loads in the first three stations is greater than the other stations. Using the lane A stake station as an initial origin, the tipping moments for each lane and station can be determined. These calculations are shown on Appendix pages 2-6. For example, because lane B is disposed along the X-axis, there are no X moment arms for the lane A tool stations. Further, the ram center is disposed at the location indicated. Knowing the various loads and moment arms relative to the initial origin, the loads and moment arms relative to the ram center can be determined as shown on Appendix A, page 7. Because these loads are not balanced, the ram press includes “kiss blocks” disposed at locations spaced from the ram center (three identified). When the kiss blocks are deflected, they create a counter force that balances the ram forces. That is, opposing kiss blocks are disposed on the upper tool assembly and the lower tool assembly. Generally, the kiss blocks contact each other as the upper tool assembly moves into the second position and level the tooling stations.
That is, a kiss block is disposed between each die shoe and each upper and lower tool member. A kiss block is made of hardened steel. A kiss block is disposed at a tool station where the final product specification must be held within 0.0001 inch. As an upper tooling element comes down, the kiss blocks engage and are deflected by as much as 0.025″. That is, the upper tooling assembly and the lower tooling assembly have, at the second position, a minimum spacing. Just before the upper tooling assembly and the lower tooling assembly reach the minimum spacing, the kiss blocks engage each other. The distance the upper tooling assembly and the lower tooling assembly move between the time the kiss blocks engage each other and their second position is, as used herein, the “deflection” or “interference” of the kiss blocks. During the time of the interference, the kiss blocks are deformed not unlike a marshmallow is deformed under pressure.
The amount of deflection is set prior to forming operations. Typically, the tool assemblies are moved into the second position and the relative positions of the upper and lower tool assemblies are adjusted so that the kiss blocks are deflected. This adjustment is identified as “pre-load.” The pre-load deflection of kiss blocks in different locations are not always the same. For example, when the unload side (downstream, finished product side) kiss blocks are pre-loaded with a 0.025 inch deflection, the load side (upstream, unfinished side) kiss blocks are between about 0.009 inch and 0.011 inch, or about 0.010 inch deflection. The deflection of the kiss blocks removes substantially all deflection out of the ram and also takes up any linkage/bearing clearances in the press. In this configuration, the kiss blocks ensure that the upper tooling is substantially flat and parallel to the bottom tooling. It also ensures that the residual of any end stock between the upper and lower tooling, such as a score, is maintained to as accurate as +/−0.00045 inch (i.e. a 0.0009 inch range). When the die assemblies separate, the kiss blocks vibrate while returning to their original shape. This vibration, known as “snap through,” causes wear and tear on the conversion press. The snap through vibration is increased when the deflection is greater.
The unbalanced forces, and the associated wear and tear, the size of the ram and associated drive, and the potential for fluids dripping on the can ends are problems with known presses. The degree to which the kiss blocks are deflected, i.e. the amount of deflection of the kiss blocks, is also a disadvantage.